COA cant block sound
But how though?
Without prep Shanks cant do anything, all Apoo has to do is kite him until he deals enough damage to take him down
The DF converts sound into physical attacks..So yes CoA hardening can defend against Appo's DF ability......Luffy was slapped..& Zoro was slashed...why is that damage not nullified/blocked if their skin was hardened???? They couldn't perceive theattack that's a reason beside Oda not wanting them to harden, as to why they didn't...
Shanks isnt some random strong Pirate. He's a Yonkou. So yes Appo's DF can catch you off guard and you'll most likely receive the attack..Shanks reaction isnt going to be Zoro's reaction..and that if Shanks doesnt possess monster level defense, which should be highly assumed looking at how tough someone like Doffy was.
Anyway, Shanks will come up with a strategy in no time, he can plug his ears with something, or simply Blitz Appo's life away...There's a huge gap in every stat I'm sure of that. Appo doesnt survive the fight..
The match up is kute. And funny but let's not troll. Appo isnt beating the 1 arm Yonkou...Appo isnt even all that strong, his DF is just almost haxxish.